Method and system for compensating engine thermal conditions

ABSTRACT

A method for compensating for thermal transient conditions of an engine that can cause valve growth or contraction is disclosed. In one example, the method provides cylinder air amount compensation during non-blow-through and blow-through conditions. The approach may improve cylinder air amount estimates, thereby improving engine emissions.

BACKGROUND/SUMMARY

Direct acting mechanical bucket (DAMB) valve actuators may be producedwith no valve lash adjustment. As such, DAMB operated valves may respondquickly, however, temperature changes occurring within the engine havingDAMB operated valves may cause expansion or contraction of valvesresulting in changes to valve event timing. For example, a change inengine load can cause engine temperatures and pressures to increase. Theincreased cylinder temperature can cause exhaust valve expansion.Further, the cylinder head may also expand, and the exhaust valveexpansion rate may be different from the cylinder head expansion ratebecause the exhaust valve and the cylinder head may be formed fromdifferent materials or because the exhaust valves are cooled differentlyfrom the cylinder head. The temperature changes in the cylinder maycause changes in valve stem length and valve diameter. As a result,valve timing changes may occur by way of a valve opening and/or closingat different times as valve temperature and cylinder head temperaturechange. Consequently, volumetric efficiency of the engine may changeduring transient engine operating conditions where valve and/or cylinderhead temperatures change due to changes in engine operating conditions.

The inventors herein have recognized the above-mentioned disadvantagesand have developed a method of compensating for thermal conditionsduring transient engine conditions, comprising: adjusting an engine airamount parameter and a cylinder residual gas amount via an engine MAPand cylinder air amount volumetric efficiency relationship in responseto a rate of change of cylinder air amount; and adjusting output of anengine actuator in response to the engine air amount parameter.

By adjusting cylinder air amount and a cylinder residual gas amount viaan engine manifold absolute pressure (MAP) and cylinder air amountvolumetric efficiency relationship in response to a rate of change ofcylinder air amount, it may be possible to account for valvetemperatures that can affect engine volumetric efficiency. The change ofcylinder air amount may be indicative of a valve temperature change sothat cylinder air amount and cylinder residual gas may be compensateduntil the engine reaches an equilibrium temperature where the MAP andcylinder air amount relationship may be used without compensation.

The present description may provide several advantages. In particular,the approach can reduce vehicle emissions by providing improved engineair-fuel control. Further, the approach may also reduce engine misfiresand/or slow combustion events which also may increase engine emissions.Further still, the approach provides a simple way to compensate cylinderair amount and cylinder exhaust residuals during transient engineoperating conditions.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic depiction of an engine;

FIG. 2 shows a plot of simulated error on cylinder air amount, residualgas, and blow-through air caused by valve temperature related totransient engine operating conditions;

FIG. 3 shows a high level block diagram of a method for compensatingvalve temperature;

FIG. 4 shows a plot illustrating compensation for cylinder volumetricefficiency impacting cylinder air amount and cylinder exhaust gasdilution as determine from MAP;

FIG. 5 shows a plot illustrating compensation for cylinder volumetricefficiency impacting inferred manifold pressure as determined from MAF;and

FIG. 6 shows a flowchart of an example method compensating for exhaustvalve timing changes during transient conditions.

DETAILED DESCRIPTION

The present description is directed to adjusting cylinder air amount andcylinder residual gas amount of a cylinder of an engine. FIG. 1 showsone example system for adjusting cylinder air amount of a cylinder. Insome examples, the system may include a turbocharger with a sparkignited mixture of air and gasoline, alcohol, or a mixture of gasolineand alcohol. However, in other examples, the engine may be a compressionignition engine, such as a diesel engine. FIG. 2 shows a simulatedexample plot of curves that are the basis for compensating cylinder airamount and cylinder residual amount.

FIG. 3 shows an example method for adjusting cylinder air amount. Visualexamples of how cylinder air amount, MAP, and cylinder residual amountare adjusting according to the method disclosed herein are shown inFIGS. 4-5. A flowchart of a method for adjusting cylinder air amount andcylinder residual gas amount is shown in FIG. 6.

Referring to FIG. 1, internal combustion engine 10, comprising aplurality of cylinders, one cylinder of which is shown in FIG. 1, iscontrolled by electronic engine controller 12. Engine 10 includescombustion chamber 30 and cylinder walls 32 with piston 36 positionedtherein and connected to crankshaft 40. Combustion chamber 30 is showncommunicating with intake manifold 44 and exhaust manifold 48 viarespective intake valve 52 and exhaust valve 54. Each intake and exhaustvalve may be operated by an intake cam 51 and an exhaust cam 53.Alternatively, one or more of the intake and exhaust valves may beoperated by an electromechanically controlled valve coil and armatureassembly. The position of intake cam 51 may be determined by intake camsensor 55. The position of exhaust cam 53 may be determined by exhaustcam sensor 57.

Fuel injector 66 is shown positioned to inject fuel directly intocombustion chamber 30, which is known to those skilled in the art asdirect injection. Alternatively, fuel may be injected to an intake port,which is known to those skilled in the art as port injection. Fuelinjector 66 delivers liquid fuel in proportion to the pulse width ofsignal FPW from controller 12. Fuel is delivered to fuel injector 66 bya fuel system (not shown) including a fuel tank, fuel pump, and fuelrail (not shown). Fuel injector 66 is supplied operating current fromdriver 68 which responds to controller 12. In addition, intake manifold44 is shown communicating with optional electronic throttle 62 whichadjusts a position of throttle plate 64 to control air flow from intakeboost chamber 46.

Exhaust gases spin turbocharger turbine 164 which is coupled toturbocharger compressor 162 via shaft 161. Compressor 162 draws air fromair intake 42 to supply boost chamber 46. Thus, air pressure in intakemanifold 44 may be elevated to a pressure greater than atmosphericpressure. Consequently, engine 10 may output more power than a normallyaspirated engine.

Distributorless ignition system 88 provides an ignition spark tocombustion chamber 30 via spark plug 92 in response to controller 12.Ignition system 88 may provide a single or multiple sparks to eachcylinder during each cylinder cycle. Further, the timing of sparkprovided via ignition system 88 may be advanced or retarded relative tocrankshaft timing in response to engine operating conditions.

Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled toexhaust manifold 48 upstream of exhaust gas after treatment device 70.Alternatively, a two-state exhaust gas oxygen sensor may be substitutedfor UEGO sensor 126. In some examples, exhaust gas after treatmentdevice 70 is a particulate filter and/or a three-way catalyst. In otherexamples, exhaust gas after treatment device 70 is solely a three-waycatalyst.

Exhaust gases may be routed from downstream of turbine 164 to upstreamof compressor 162 via exhaust gas recirculation (EGR) valve 80. Inanother example, exhaust gases may be routed from upstream of turbine164 to downstream of compressor 162. Further, engine combustion chamber30 may contain residual exhaust from a prior combustion event thatremains in combustion chamber during a subsequent cylinder cycle. Thus,combustion chamber 30 may include internal (e.g., exhaust gases thatremain in the cylinder from one combustion event to the next) EGR andexternal EGR via EGR valve 80.

Controller 12 is shown in FIG. 1 as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106, random access memory 108, keep alive memory 110, and aconventional data bus. Controller 12 is shown receiving various signalsfrom sensors coupled to engine 10, in addition to those signalspreviously discussed, including: engine coolant temperature (ECT) fromtemperature sensor 112 coupled to cooling sleeve 114; a position sensor134 coupled to an accelerator pedal 130 for sensing accelerator positionadjusted by foot 132; a knock sensor for determining ignition of endgases (not shown); a measurement of engine manifold pressure (MAP) frompressure sensor 121 coupled to intake manifold 44; a measurement ofboost pressure from pressure sensor 122 coupled to boost chamber 46; anengine position sensor from a Hall effect sensor 118 sensing crankshaft40 position; a measurement of air mass entering the engine from sensor120 (e.g., a hot wire air flow meter); and a measurement of throttleposition from sensor 58. Barometric pressure may also be sensed (sensornot shown) for processing by controller 12. In a preferred aspect of thepresent description, engine position sensor 118 produces a predeterminednumber of equally spaced pulses every revolution of the crankshaft fromwhich engine speed (RPM) can be determined.

In some embodiments, the engine may be coupled to an electricmotor/battery system in a hybrid vehicle. The hybrid vehicle may have aparallel configuration, series configuration, or variation orcombinations thereof. Further, in some embodiments, other engineconfigurations may be employed, for example a diesel engine.

During operation, each cylinder within engine 10 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54 closes and intake valve 52 opens. Air isintroduced into combustion chamber 30 via intake manifold 44, and piston36 moves to the bottom of the cylinder so as to increase the volumewithin combustion chamber 30. The position at which piston 36 is nearthe bottom of the cylinder and at the end of its stroke (e.g. whencombustion chamber 30 is at its largest volume) is typically referred toby those of skill in the art as bottom dead center (BDC). During thecompression stroke, intake valve 52 and exhaust valve 54 are closed.Piston 36 moves toward the cylinder head so as to compress the airwithin combustion chamber 30. The point at which piston 36 is at the endof its stroke and closest to the cylinder head (e.g. when combustionchamber 30 is at its smallest volume) is typically referred to by thoseof skill in the art as top dead center (TDC). In a process hereinafterreferred to as injection, fuel is introduced into the combustionchamber. In a process hereinafter referred to as ignition, the injectedfuel is ignited by known ignition means such as spark plug 92, resultingin combustion. During the expansion stroke, the expanding gases pushpiston 36 back to BDC. Crankshaft 40 converts piston movement into arotational torque of the rotary shaft. Finally, during the exhauststroke, the exhaust valve 54 opens to release the combusted air-fuelmixture to exhaust manifold 48 and the piston returns to TDC. Note thatthe above is described merely as an example, and that intake and exhaustvalve opening and/or closing timings may vary, such as to providepositive or negative valve overlap, late intake valve closing, orvarious other examples.

Turbocharged and supercharged engines pressurize air entering an engineso that engine power may be increased. The pressurized air provides foran increased cylinder air charge during a cycle of the engine ascompared to a naturally aspirated engine. Further, the cylinder fuelcharge can be increased as the cylinder air charge is increased toincrease the amount of energy produced when the fuel is combusted withthe air during a cycle of the cylinder. However, during periods of valveoverlap where both intake and exhaust valves of a cylinder aresimultaneously open, it is possible for air to pass directly from theengine intake manifold to the engine exhaust manifold withoutparticipating in combustion within a cylinder. Air passing directly fromthe intake manifold to the exhaust manifold without participating incombustion may be referred to as blow-through.

Thus, the system of FIG. 1 provides for an engine system, comprising: anengine; a turbocharger coupled to the engine; and a controller includinginstructions for adjusting an engine air amount parameter and a cylinderresidual gas amount in response to a rate of change of cylinder airamount flow during blow-through and non-blow-through engine operatingconditions, the controller including further instructions for adjustingan actuator in response to the engine air amount parameter. Thus, thesystem provides compensation for both blow-through and non-blow-throughconditions.

The engine system further comprises adjusting a residual gas amountbased on the adjusted engine air amount parameter. The engine systemalso includes where the rate of change of cylinder air amount flow isdetermined from a difference between engine air flow and filtered engineair flow. The engine system further comprises additional instructionsfor adjusting the engine air amount parameter in response to cam timing.The engine system further comprises additional instructions foradjusting the engine air amount parameter in response to engine speedand engine load. In another example, the engine system further comprisesadditional instructions to determine blow-through during cylinder airflow conditions where cylinder air flow is greater than a cylinder airflow at an intersection of a maximum volumetric efficiency curve and anon-blow-through curve.

Referring now to FIG. 2, a plot of simulated error on cylinder airamount, residual gas, and blow-through air caused by transient thermalengine operating conditions is shown. The X axis of plot 200 representsair mass amount of a cylinder per cylinder intake event or cylindercycle. Air mass amount increases from the left side of the plot to theright side of the plot. The Y axis of plot 200 represents engine intakemanifold absolute pressure (MAP) and MAP increase from the bottom of theorigin of the plot in a direction of the Y axis. Vertical marker 250represents a cylinder air amount where air blow-through occurs ifcylinder air amount increases to the right of vertical marker 250, andwhere air blow-through does not occur to the left of vertical marker250. Vertical marker 250 passes through the intersection of curves 202and 206 which may be used to identify blow-through conditions viacomparing cylinder air flow to the air flow at the intersection ofcurves 202 and 206

Curve 202 represents the theoretical maximum air amount (e.g., 100%volumetric efficiency) that the cylinder can hold at a given pressure atintake valve closing (IVC). Thus, the cylinder mass amount increaseslinearly as the cylinder pressure increases. In one example, the maximumair amount that the cylinder can hold may be characterized as a slope ofa line where the slope is described as:

${Slope} = \frac{1}{\left( {1 - r_{pb}} \right)c_{norm}}$where variable c_(norm) accounts for physical properties of air, intakemanifold temperature, and cylinder displacement. Variable r_(pb) is aneffective pushback ratio characterizing a portion of a cylinder mixturethat may be pushed into the engine intake manifold from the cylinder asthe piston moves in a direction toward the cylinder head while theintake valve is open. The pushback ratio may be determined as thegreater of a constant multiplied by the physical ratio of cylindervolume displaced by the piston moving from bottom dead center (BDC) tothe intake valve closing (IVC) point, to the total cylinder displacementvolume of the cylinder and the pushback ratio computed from enginemapping as:

$1 - \frac{1}{c_{norm}*{air\_ slope}}$where air_slope is the least-squares linear fit of the manifold pressurevs. trapped air amount data excluding blow-through data points.

Curve 204 represents a cylinder air amount vs. MAP volumetric efficiencyrelationship during cold engine operating conditions where engine and/orcylinder valve temperature are less than at nominal (e.g. steady-state)engine operating conditions. During cool conditions, cylinder valves mayexpand less than during conditions where the engine is operating atnominal engine temperature (e.g., 90° C.). As a result, exhaust gasresiduals held in a cylinder after a compression stroke of the cylinderand into a subsequent compression stroke of the cylinder may decrease ascompared to nominal engine operating conditions.

Curve 206 represents a cylinder air amount vs. MAP volumetric efficiencyrelationship during nominal mapped engine operating conditions that arestored in controller memory where engine temperature and cylinder valvetemperature have time to stabilize. In particular, curve 206 representssteady state engine speed and load conditions.

Curve 208 represents a cylinder air amount vs MAP volumetric efficiencyrelationship during warm engine operating conditions where engine and/orcylinder valve temperature are greater than at nominal engine operatingconditions. During warm conditions, cylinder valves may expand more thanduring conditions where the engine is operating at nominal enginetemperature. Consequently, exhaust gas residuals held in a cylinderafter an intake stroke of the cylinder and into a subsequent compressionstroke of the cylinder may increase as compared to nominal engineoperating conditions.

It can be seen that curve 206 exhibits a lower cylinder air amount foran equivalent MAP as compared to curve 202 for cylinder air amounts lessthan or to the left of vertical marker 250. The lower cylinder airamount may be attributed to residual exhaust gases remaining in thecylinder from a previous combustion event.

The engine controller includes a function or table containing valuesthat represent curves 206 and 202. The engine controller may alsocontain curves 208 and 204 as well as curves for other enginetemperatures; however, storing and retrieving additional curves cancomplicate, slow down, and increase the cost of the controller. Inaddition, relationship between the cylinder air amount and MAPrepresented by the curves 204 and 208 can only be observed during largetransients, which makes their characterization more difficult comparedto the nominal relationship described by curve 206. Therefore, it can bebeneficial to compensate curve 206 for the conditions that providecurves 204 and 208 according to the methods of FIGS. 3 and 6. Thus,cylinder air amount and cylinder residual gas amount can be determinedby interpreting curve 206 and adjusting for the engine operatingconditions so as to follow curves 204 and 208.

Two examples are provided to illustrate how valve and engine temperatureaffect cylinder air amount and cylinder exhaust gas residual amount.Similar relationships occur to the right of vertical marker 250 betweencurves 202 and 208; however, the distance between curve 202 and curves204-208 represent different amounts of blow-through air (e.g., air thatblows through a cylinder when intake manifold pressure is greater thanexhaust pressure while intake and exhaust valves of a cylinder aresimultaneously open).

Horizontal marker 260 represents a first constant intake manifoldpressure. Horizontal marker 260 intersects curve 202 at 261. If avertical line is extended from 261 to the X axis, a cylinder air amountmay be determined at the intersection of the vertical line and the Xaxis. Cylinder air amount at 261 represents a condition of 100% cylindervolumetric efficiency (e.g., the theoretical amount of air a cylindercan hold) when the engine is operated at a MAP of horizontal marker 260and at the nominal air temperature. Cylinder air amount at 262represents cylinder air amount at nominal engine operating conditionswhere the relationship between MAP and cylinder air amount is mapped. Ifa vertical line is extended from 262 to the X axis, cylinder air amountfor nominal mapped conditions may be determined at the intersection ofthe vertical line and the X axis. Cylinder air amount at 263 representscylinder air amount at warm engine operating conditions where therelationship between MAP and cylinder air amount is compensated by themethods of FIGS. 3 and 6. If a vertical line is extended from 263 to theX axis, cylinder air amount for warm conditions may be determined at theintersection of the vertical line and the X axis.

The distance between arrows 264 represents a difference in cylinder airamount between nominal engine mapping conditions and warm engineoperating conditions at MAP level 260. In particular, when the engine isoperated warm at low load conditions (warmer than steady-state operatingtemperatures for this condition), cylinder air amount is over estimatedbecause cylinder air amount at nominal engine operating conditions(e.g., 262) is greater cylinder air amount at warm operating conditions(e.g., 263). Thus, cylinder air amount will be overestimated via mappedcurve 206 unless compensation is provided to adjust cylinder air amountto 263 during warm engine operating conditions.

Distance 266 represents an amount of exhaust gas residuals in a cylinderduring a cycle of the cylinder for warm engine operating conditions whenMAP is at the level of horizontal marker 260. The amount of exhaust gasresiduals in a cylinder for warm engine operating conditions can bedetermined at the MAP level of 260 via subtracting the cylinder air massat 263 of warm volumetric efficiency curve 208 of from the cylinder airmass at 261 of maximum volumetric efficiency curve 202. Distance 268represents an amount of exhaust gas residuals in a cylinder during acycle of the cylinder for nominal engine operating conditions. Theamount of exhaust gas residuals in a cylinder for nominal operatingconditions at MAP level 260 can be determined via subtracting thecylinder air mass at 262 of nominal volumetric efficiency curve 206 fromthe cylinder air mass at 261 of maximum volumetric efficiency curve 202.

Horizontal marker 280 represents a second constant MAP. Horizontalmarker 280 intersects maximum volumetric efficiency curve 202 at 281. Ifa vertical line is extended from 281 to the X axis, a cylinder airamount may be determined at the intersection of the vertical line andthe X axis. Cylinder air amount at 281 represents a condition of 100%cylinder volumetric efficiency when the engine is operated at a MAP ofhorizontal marker 280. Cylinder air amount at 282 represents cylinderair amount at cold engine operating conditions where the relationshipbetween MAP and cylinder air amount is compensated by the methods ofFIGS. 3 and 6. If a vertical line is extended from 282 to the X axis,cylinder air amount for cold conditions may be determined at theintersection of the vertical line and the X axis. Cylinder air amount at283 represents cylinder air amount at nominal engine operatingconditions where the relationship between MAP and cylinder air amount ismapped. If a vertical line is extended from 283 to the X axis, cylinderair amount for nominal mapped conditions may be determined at theintersection of the vertical line and the X axis.

The distance between arrows 284 represents a difference in cylinder airamount between nominal engine mapping conditions and cold engineoperating conditions when MAP is at 280. In particular, when the engineis operated cold at medium load conditions, cylinder air amount is underestimated because cylinder air amount at nominal engine operatingconditions (e.g., 283) is less than cylinder air amount at coldoperating conditions (e.g., 282). Thus, cylinder air amount will beunderestimated via curve 206 unless compensation is provided to adjustcylinder air amount to 283 during cold engine operating conditions.

Distance 286 represents an amount of exhaust gas residuals in a cylinderduring a cycle of the cylinder for nominal engine operating conditionswhen MAP is at the level of horizontal marker 280. The amount of exhaustgas residuals in a cylinder for nominal engine operating conditions canbe determined via subtracting the cylinder air mass at 283 of nominalvolumetric efficiency curve 206 from the cylinder air mass at 281 ofmaximum volumetric efficiency curve 202. Distance 288 represents anamount of exhaust gas residuals in a cylinder during a cycle of thecylinder for cold engine operating conditions. The amount of exhaust gasresiduals in a cylinder for cold operating conditions can be determinedvia subtracting the cylinder air mass at 282 of cold volumetricefficiency curve 204 from the cylinder air mass at 281 of nominalvolumetric efficiency curve 202.

Thus, it can be observed from FIG. 2 that when cylinder air amount isestimated according to curve 202, cylinder air amount will beunderestimated when the engine and valves are cold if compensation isnot provided. Further, it can be observed that the exhaust gas residualamount estimated in a cylinder will be overestimated when the engine andvalves are cold if compensation is not provided. Similarly, cylinder airamount will be overestimated when the engine and valves are warmer thannominal conditions if compensation is not provided. Additionally, theexhaust gas residual amount estimated in a cylinder will beunderestimated when the engine and valves are warmer than nominalconditions if compensation is not provided.

Referring now to FIG. 3, a high level block diagram of a method forcompensating valve temperature is shown. The method of FIG. 3 may beimplemented via instructions in a controller of a system as shown inFIG. 1.

At 302, method 300 judges whether or not a condition of blow-throughexits. In one example, method 300 may judge that blow-through existswhen air flow into a cylinder exceeds a cylinder air amount described bya maximum cylinder volumetric efficiency curve (e.g., to the right ofvertical marker 250 of FIG. 2). If a blow-through estimate is determinedto be less than or equal to zero (e.g., a non-blow-through condition), avalue of one is output at 302. Otherwise, if the blow-through estimateis determined to be greater than zero, a value of zero is output at 302.

At 304, a base non-blow-through gain is determined. The base gain amountmay be empirically determined and stored in a table that is indexed byengine speed, engine load, and engine temperature. The output of 304 and302 are multiplied at junction 306.

At 308, engine air flow and engine speed are used to determine air flowrate. In one example, air flow rate is determined by integrating engineair flow during a selected engine rotation interval (e.g., one cylindercycle) and multiplying the result by an engine speed factor (e.g.,conversion from engine speed to cylinder strokes) to determine cylinderair amount per cylinder stroke. In other examples, an air flow rate inother units may be provided. An air flow rate is directed from 308 to310.

At 310, method 300 filters the air flow rate output of 308. In oneexample, a low pass filter with a higher cut-off frequency may beapplied to the air flow rate. The filtered air flow rate is directed tosumming junction 314 and low pass filter 312. Low pass filter 312 may bea first-order or higher order filter. Low pass filter 312 may include anadjustable time constant that is based on engine operating conditions.For example, low pass filter 312 may have a first time constant at lowerengine temperatures and a second time constant for higher enginetemperatures.

At 314, method 300 subtracts the low pass filtered air flow rate fromthe non-low pass filtered air flow rate. Subtracting the low passfiltered air flow rate from the air flow rate provides a rate of changeof air flow rate. The rate of change in the air flow rate is directed to316.

At 318, engine speed indexes a function of empirically determined gainthat accounts for an engine speed dependency in the air amountadjustment for changes in engine temperature. The output of 318 isdirected to 316.

At 320, engine speed indexes a function of empirically determined gainthat accounts for engine valve overlap relative to top-dead-centerexhaust stroke. The output of 320 is directed to 316.

At 322, engine speed indexes a function of empirically determined gainthat accounts for engine valve overlap duration. The output of 322 isdirected to 316.

At 324, engine speed indexes a function of empirically determined gainthat accounts for an engine load dependency in the air amount adjustmentfor changes in engine temperature. The output of 324 is directed to 316.

At 316, the outputs of 306, 314, 318, 320, 322, and 324 are multipliedtogether to provide a non-blow-through volumetric efficiency correction.Thus, if the output of 302 is a value of one, a value other than zeromay be output from 316. If the output of 302 is zero, non-blow-thoughcompensation is not provided. In this way, the non-blow-throughvolumetric efficiency can be zeroed when blow-through occurs.

For the blow-through volumetric efficiency correction, the blow-throughair estimate is passed directly to 334. The blow-though air may bedetermined as described above.

At 326, engine air flow and engine speed are used to determine air flowrate as described at 308. An air flow rate is directed from 326 to 328.At 328, method 300 filters the air flow rate output of 326 as describedat 310. However, a different filter and/or filter time constant may beprovided at 328. The filtered air flow rate is directed to summingjunction 332 and low pass filter 330. Low pass filter 330 may be afirst-order or higher order filter as described at 312. However, lowpass filter 330 may have a time constant that is different from the timeconstant of low pass filter 312.

At 332, method 300 subtracts the low pass filtered air flow rate fromthe non-low pass filtered air flow rate. Subtracting the low passfiltered air flow rate from the air flow rate provides a rate of changeof air flow rate. The rate of change in the air flow rate is directed to334.

At 336, engine speed indexes a function of empirically determined gainthat accounts for an engine speed dependency in the air amountadjustment for changes in engine temperature. The values at 336 may bedifferent than the values at 318. The output of 336 is directed to 334.

At 338, engine speed indexes a function of empirically determined gainthat accounts for engine valve overlap. The values at 338 may bedifferent than the values at 320. The output of 338 is directed to 334.

At 340, engine speed indexes a function of empirically determined gainthat accounts for engine valve overlap duration. The values at 340 maybe different than the values at 322. The output of 340 is directed to334.

At 342, engine load indexes a function of empirically determined gainthat accounts for an engine load dependency in the air amount adjustmentfor changes in engine temperature. The values at 342 may be differentthan the values at 324. The output of 342 is directed to 334.

At 334, the blow-through air estimate and the outputs of 332, 336, 338,340, and 342 are multiplied together to provide a blow-throughvolumetric efficiency correction. Thus, if the blow-through amount isnon-zero, a value other than zero may be output from 334. If theblow-through amount is zero, blow-though compensation is not provided.In this way, the blow-through volumetric efficiency correction can beoutput when blow-through occurs.

At 350, the blow-through volumetric efficiency correction and thenon-blow-through volumetric efficiency correction amounts are summed.However, because of the way method 300 is structured, either theblow-through compensation or the non-blow-through compensation will bezeroed out so that only blow-through or non-blow-through compensation isprovided. The output of 350 is directed to an engine air amountparameter compensation method where an engine air amount parameter(e.g., cylinder air amount or blow-through air amount) and cylinderresidual exhaust gases are determined via curves similar to curves 202and 206 of FIG. 2. In particular, if MAP is known, cylinder air amountis determined by indexing a function similar to that of FIG. 2 with MAPand the cylinder air amount value output is then added with thecompensation output of 350. The exhaust gas residual is determined bysubtracting the cylinder air amount from the maximum cylinder air amountat a MAP value as described with regard to FIG. 2 via curve 202. In thisway, the cylinder air amount and residual exhaust amount may bedetermined. Further, the cylinder air amount reduction or increase isphased out as time increases from the transient condition. The phase outof cylinder air amount change emulates conditions of a valve thermaltransient.

In other examples, where cylinder air mass is measured, MAP may bedetermined via indexing a table or function similar to FIG. 2 whichoutputs MAP for the determined cylinder air amount. The residual gasamount may be determined as previously described.

Referring now to FIG. 4, a plot illustrating thermal compensation forcylinder volumetric efficiency impacting cylinder air amount andcylinder exhaust gas dilution is shown. The method described herein isexecutable via instructions of a controller in a system such as in FIG.1 and useful for systems that measure mass air flow and is included inthe method of FIG. 6.

The X axis represents cylinder air amount and cylinder air amountincreases from the left side of the plot to the right side of the plot.The Y axis represents MAP and MAP increases from the X axis in thedirection of the Y axis arrow. Vertical marker 450 indicates where airblow-through can occur. Specifically, blow-through can occur whencylinder air flow is greater than or to the right of the level indicatedby vertical marker 450. Blow-thorough is not present during cylinder airflows that are to the left of vertical marker 450.

In the example of FIG. 4, volumetric efficiency compensation for valvetemperature changes during a load change from a lower load to a higherload where valve temperature increases is shown. In this example, thecylinder air amount increases due to compensation for increasing valvetemperature.

Further in this example, cylinder air amount increases from a low levelto the level shown by vertical marker 404. Vertical marker 404represents a mapped base cylinder air amount that is uncompensated anddetermined via a MAP sensor, for example. Cylinder air amount may beestimated at a level shown by vertical marker 404 by indexing a table orfunction via MAP at the level of 402 to output cylinder air amount atthe level 404 according to curve 430 (e.g. a mapped non-blow-throughcurve describing cylinder volumetric efficiency based on MAP andcylinder air amount). The base estimated cylinder exhaust gas dilutionis determined as the difference between the value of curve 430 at 404and the value of curve 431 at 408, where curve 431 represents themaximum level or theoretical cylinder volumetric efficiency. The baseestimated cylinder exhaust gas dilution is indicated by arrow 422.

The volumetric efficiency compensation described in FIGS. 3 and 6 isadded to the cylinder air amount represented by vertical marker 404 toprovide compensated cylinder air amount as indicated by vertical marker406. The amount of cylinder air amount compensation is represented byarrow 420. The compensated estimated cylinder exhaust gas dilution isdetermined as the difference between the value of curve 430 at theintersection with vertical marker 406 and the value of curve 431 at theintersection with vertical marker 408. The compensated estimatedcylinder exhaust gas dilution is indicated by arrow 424.

The cylinder air amount compensation shown in FIG. 4 impacts estimatedMAP by providing an increased cylinder air amount for a lower MAP. Thus,the compensated cylinder air amount is determined from a base cylinderair amount as determined from MAP added to an amount of cylinder airamount compensation.

Referring now to FIG. 5, a plot illustrating thermal compensation forcylinder volumetric efficiency impacting MAP is shown. The methoddescribed herein is executable via instructions of a controller in asystem such as in FIG. 1 and useful for systems that measure MAP and isincluded in the method of FIG. 6.

The X axis represents cylinder air amount and cylinder air amountincreases from the left side of the plot to the right side of the plot.The Y axis represents MAP and MAP increases from the X axis in thedirection of the Y axis arrow. Vertical marker 550 indicates where airblow-through can occur. Specifically, blow-through can occur whencylinder air flow is greater than or to the right of the level indicatedby vertical marker 550. Blow-thorough is not present during cylinder airflows that are to the left of vertical marker 550.

In the example of FIG. 5, volumetric efficiency compensation for valvetemperature changes during a load change from a lower load to a higherload where valve temperature increases is shown. In this example, thecylinder air amount increases due to compensation for increasing valvetemperature.

Further in this example, cylinder air amount increases from a low levelto the level shown by vertical marker 508. Vertical marker 508represents a mapped base cylinder air amount that is uncompensated anddetermined via a mass air flow meter, for example. MAP may be estimatedat a level shown by horizontal marker 502 by indexing a table orfunction to output MAP at the level of 502 based on cylinder air amountat 508 according to curve 530 (e.g. a mapped non-blow-through curvedescribing cylinder volumetric efficiency based on MAP and cylinder airamount). The base estimated cylinder exhaust gas dilution is determinedas the difference between the value of curve 530 at 508 and the value ofcurve 531 at 510, where curve 531 represents the maximum level ortheoretical cylinder volumetric efficiency. The base estimated cylinderexhaust gas dilution is indicated by arrow 522.

The volumetric efficiency compensation described in FIGS. 3 and 6 isadded to the cylinder air amount represented by vertical marker 508 tocompute a temporary cylinder air amount that is the basis for revisingMAP. The temporary cylinder air amount is indicated by vertical marker506 and is not a basis for adjusting the cylinder fuel amount. Theamount of cylinder air amount compensation is represented by arrow 520.MAP at the level of 504 is determined via indexing curve 530 using thetemporary cylinder air amount. The compensated estimated cylinderexhaust gas dilution is determined as the difference between the valueof curve 530 at the intersection with vertical marker 506 and the valueof curve 531 at the intersection with vertical marker 511. Thecompensated estimated cylinder exhaust gas dilution is indicated byarrow 524.

Referring now to FIG. 6, a method for compensating for exhaust valvetiming changes during transient conditions due to thermal conditions isshown. The method of FIG. 6 is executable via instructions of acontroller in a system as shown in FIG. 1.

At 602, method 600 determines engine operating conditions. Engineoperating conditions may include but are not limited to engine speed,engine load, engine intake manifold pressure, engine air flow rate,engine temperature, and cam position. Method 600 proceeds to 604 afterengine operating conditions are determined.

At 604, method 600 judges whether cylinder air amount is based on MAP orMAF sensor inputs. If cylinder air amount is based on MAP YES isanswered at 604 and method 600 proceeds to 606. Otherwise, NO isanswered at 604 and method 600 proceeds to 608.

At 608, method 600 determines a base cylinder air amount from a mass airflow (MAF) sensor, and MAP is determined via indexing a table orfunction that includes a cylinder volumetric efficiency relationshipcurve according to a MAP cylinder air amount relationship (e.g., curve530 of FIG. 5) using cylinder air amount as determined from the MAFsensor. The table outputs a base MAP. Further, a base cylinder exhaustgas residual may be determined via subtracting a cylinder air amountdetermined from the cylinder volumetric efficiency relationship curve(e.g., curve 530 of FIG. 5) from a maximum cylinder air amountdetermined from a theoretical cylinder air amount curve (e.g., 531 andresidual amount 524 of FIG. 5) at the MAP level determined from cylinderair amount. Method 600 proceeds to 610 after based values of cylinderair amount, MAP, and cylinder exhaust gas residual are determined.

At 606, method 600 determines a base cylinder air amount from a MAPsensor via indexing a table or function that includes a cylindervolumetric efficiency relationship curve according to a MAP cylinder airamount relationship (e.g., curve 430 of FIG. 4) using MAP. The tableoutputs a base cylinder air amount. Further, a base cylinder exhaust gasresidual may be determined via subtracting a cylinder air amountdetermined from the cylinder volumetric efficiency relationship curvefrom a maximum cylinder air amount determined from a theoreticalcylinder air amount curve (e.g., curve 431 of FIG. 4 and residual amount422) from the MAP determined from the MAP sensor. Method 600 proceeds to610 after based values of cylinder air amount, MAP, and cylinder exhaustgas residual are determined.

At 610, method 600 judges whether or not blow-through is present at thecurrent engine operating conditions. In one example, blow-through may bedetermined when air flow into a cylinder exceeds a cylinder air amountdescribed by a maximum cylinder volumetric efficiency curve (e.g., tothe right of vertical marker 550 of FIG. 5). For example, if thecylinder air amount from curve 530 at a MAP level is subtracted from themaximum cylinder volumetric efficiency curve 531 for cylinder air flowat a level to the right of vertical marker 550 of FIG. 5 and the resultis negative, blow-thorough may be determined. Method 300 proceeds to 614if blow-through is not determined and the blow-through amount is set tozero. Otherwise, if the answer at 610 is yes, method 600 proceeds to612.

At 612, method 600 determines the amount of blow-through. A blow-throughamount may be determined via subtracting a maximum cylinder air amountat a MAP level from a cylinder air amount at the same MAP level when thecylinder air amount is greater than a cylinder air amount at anintersection of a maximum cylinder air amount curve and a volumetricefficiency curve that represents a cylinder air amount MAP relationshipduring mapped engine operating conditions where engine temperature andcylinder valve temperature have time to stabilize. For example, at aconstant level of MAP greater than MAP at the location where verticalmarker 550 intersects curve 531 in FIG. 5, subtracting a cylinder airamount as determined from a maximum cylinder air amount curve 531 ofFIG. 5 from cylinder air amount determined from curve 530 of FIG. 5.Method 600 proceeds to 616 after the blow-through amount is determined.

At 614, method 600 determines a base gain amount for adjusting cylinderair amount. The base gain amount may be empirically determined andstored in memory that is indexed according to engine speed and load, forexample. Method 600 proceeds to 616 after the base gain amount isdetermined.

At 616, method 600 determines a rate of change of engine or cylinder airflow rate. In one example, the rate of change of engine or cylinder airflow rate may be determined via subtracting a filtered value of engineor cylinder air flow rate from the engine or cylinder air flow rate. Inother example, other approaches such as taking a derivative of cylinderair flow rate may also be used to determine the rate of change of engineor cylinder air flow rate. Method 600 proceeds to 618 after the rate ofchange of engine or cylinder air flow rate is determined.

At 618, method 600 looks up empirically determined gain adjustments forintake and exhaust valve overlap duration, intake and exhaust valveoverlap position relative to crankshaft position, engine speed, andengine load. The gain adjustments may be empirically determined andstored in table and/or functions that are indexed via intake and exhaustvalve overlap duration, intake and exhaust overlap position relative tocrankshaft position, engine speed and engine load. Method 600 proceedsto 620 after gain adjustments are determined at 618.

At 620, method 600 multiplies the base gain, blow-through amount, rateof change of engine or cylinder air flow rate, and gain adjustments from618 to determine the volumetric efficiency correction that is to beadded to the cylinder air amount. During conditions where blow-throughis zero, the base gain from 614 is multiplied by the rate of change ofengine or cylinder air flow rate and the gain adjustments from 618. Whenblow-through is present, the blow-through amount is multiplied by therate of change of engine or cylinder air flow rate, and the gainadjustments from 618 without using the base gain amount of 614. Method600 proceeds to 622 after the volumetric efficiency correction isdetermined.

At 622, method 600 adjusts MAP, cylinder air amount, and cylinderresidual gas amount. The cylinder air amount is adjusted via adding thevolumetric efficiency correction from 620 to the cylinder air amount asdetermined at 606 or 608.

MAP is adjusted for systems that sense engine air flow rate and inferMAP. In one example, MAP is adjusted as is described in the descriptionof FIG. 5. In particular, the cylinder air amount is first measured andthen compensation is added to the cylinder air amount to account forthermal conditions. The adjusted cylinder air amount is then used toindex a curve in a table or function that represents MAP versus cylinderair amount during mapped engine conditions (e.g., curve 530 of FIG. 5).The table or function outputs the adjusted MAP value.

Cylinder air amount is adjusted for systems that sense MAP and infercylinder air amount. In one example, cylinder air amount is adjusted asis described in the description of FIG. 4. In particular, MAP ismeasured and cylinder air amount is determined via index a curve in atable or function that represents MAP versus cylinder air amount duringmapped engine conditions (e.g., curve 430 of FIG. 4). The table orfunction outputs a base cylinder air amount. The cylinder air amountcompensation is determined and added to the base cylinder air amount toprovide a compensated cylinder air amount.

Cylinder exhaust residual amounts may be determined as described in thedescription of FIGS. 4 and 5. For example, at a MAP sensed or determinedfrom cylinder air amount, base cylinder exhaust gas residual amount maybe determined by taking a difference between a maximum cylinder airamount and a mapped cylinder air amount as determined from taking adifference between a curve representing a theoretical maximum air amountthat the cylinder can hold at a given pressure at intake valve closing(IVC) (e.g., curve 431 of FIG. 4) and a curve representing a cylinderair amount MAP relationship during nominal mapped engine operatingconditions where engine temperature and cylinder valve temperature havetime to stabilize (e.g., curve 430 of FIG. 4).

Compensated cylinder exhaust residual amounts may be determined asdescribed in the description of FIGS. 4 and 5. For example, at anadjusted MAP, compensated cylinder exhaust gas residual amount may bedetermined by taking a difference between a maximum cylinder air amount(e.g., curve 431 of FIG. 4) and a mapped cylinder air amount (e.g.,curve 430 of FIG. 4) plus cylinder air amount compensation as determinedfrom taking a difference between a curve representing a theoreticalmaximum air amount that the cylinder can hold at a given pressure atintake valve closing (IVC) and a curve representing a cylinder airamount MAP relationship during nominal mapped engine operatingconditions where engine temperature and cylinder valve temperature havetime to stabilize. Method 600 proceeds to 624 after MAP, cylinder airamount, and cylinder residual gas amount are adjusted via the volumetricefficiency correction.

During conditions where blow-through is determined at a given MAP level,the amount of blow-through can be revised by adding the volumetricefficiency compensation (e.g, 350 of FIG. 3) to the air flow through theengine at the given MAP level and then subtracting the cylinder airamount described by the maximum cylinder volumetric efficiency curve atthe given MAP level.

At 624, method 600 adjusts engine actuators in response to MAP,compensated cylinder air amount, and compensated cylinder exhaustresidual amount. In one example, where cylinder air amount is increased,the engine throttle position may be reduced so that a desired enginetorque may be provided. For example, throttle position can be adjustedbased on an empirically determined throttle map that provides a throttleposition for a desired air flow rate. If the engine air flow rateincreases due to thermal conditions, the throttle may be closed toreduce cylinder air amount and to provide a desired air flow rate basedon the compensated cylinder air amount.

In another example, where the cylinder residual amount increases due tothermal conditions, an opening amount of an EGR valve may be decreasedto compensate for the additional amount of cylinder exhaust residual.Specifically, if thermal conditions increase cylinder residuals, the EGRvalve opening amount may be decreased according to the pressure acrossthe EGR valve and the amount of increase in cylinder residuals. EGRvalve flow is commonly mapped based on pressure drop across the EGRvalve and position of the EGR valve so the EGR flow can be reducedproportionally to the increase in EGR flow into the cylinder. Of course,the EGR valve may be opened further when EGR flow into the cylinderdecreases so as to better match actual cylinder EGR with desiredcylinder EGR. Additionally, position of the EGR valve can be adjustedbased on compensated MAP so that EGR flow rate more closely matchesdesired EGR flow rate. In other words, the flow rate through the EGRvalve may be based on adjusted MAP. Additionally, intake and exhaust camoverlap can be adjusted to increase or decrease cylinder exhaust gasresidual based on the compensated cylinder exhaust residual amount.

Spark timing may also be adjusted via an ignition system for compensatedcylinder air amount and cylinder exhaust residuals. In particular, thespark is provided at a crankshaft angle that is based on compensatedcylinder air amount and engine speed. Further, spark may be furtheradjusted according to a table that accounts for cylinder exhaust gasresidual amount, and the table is indexed via the compensated cylinderexhaust gas residual amount so that spark is adjusted according tocompensated cylinder exhaust gas residual amount.

Fuel injector injection amount may also be adjusted according to thecompensated cylinder air amount. For example, if the compensatedcylinder air amount increases, fuel injection amount may be increased toprovide a desired engine air-fuel ratio Likewise, if the compensatedcylinder air amount decreases, fuel injection amount may be decreased toprovide a desired engine air-fuel ratio.

During conditions where the blow-through amount increases or decreases,blow-through may be adjusted. In one example, if a change in enginethermal conditions increases an amount of engine blow-through (e.g.,when air flow into a cylinder exceeds a cylinder air amount described bya maximum cylinder volumetric efficiency curve) blow-through may bereduce via partially closing the throttle or reducing boost pressure.Method 600 proceeds to exit after engine actuators are adjusted.

Thus, the methods of FIGS. 3 and 6 provide for compensating for thermalconditions during transient engine conditions, comprising: adjusting anengine air amount parameter and a cylinder residual gas amount via anengine MAP and cylinder air amount volumetric efficiency relationship inresponse to a rate of change of cylinder air amount; and adjustingoutput of an engine actuator in response to the engine air amountparameter. The method may be particularly useful for providingcompensating due to valve timing changes resulting from temperaturechange.

The method also includes where the engine actuator is a fuel injector,and where the engine air amount parameter is based on a curveempirically determined from a plurality of engine MAP and cylinder airamount readings. The method further includes where the engine air amountparameter is adjusted in response to a curve representing enginevolumetric efficiency in a MAP versus cylinder air amount space, andwhere the curve accounts for residual exhaust gas. In some examples, themethod includes where the engine actuator is an air inlet throttle, andfurther comprising adjusting a position of an EGR valve in response tothe cylinder residual gas amount. The method also includes where therate of change of cylinder air amount is determined via a differencebetween an air flow rate and a filtered air flow rate. The methodfurther comprises adjusting the engine air amount parameter in responseto engine cam timing. The method also includes where the engine airamount parameter is a cylinder air amount estimate and where thecylinder air amount estimate is reduced when an engine temperaturetransitions from a higher temperature to a lower temperature, and wherethe engine temperature is a temperature of a valve of a cylinder.

In another example, the methods of FIGS. 3 and 6 provide for a methodcompensating for thermal conditions during transient engine conditions,comprising: adjusting an engine air amount parameter and a cylinderresidual gas amount during a condition of blow-through in response to arate of change of cylinder air amount; and adjusting an output of anengine actuator in response to the engine air amount parameter. Themethod also includes where the condition of blow-though is estimatedfrom to a difference between a total cylinder air mass flow curve and amaximum volumetric efficiency curve. The method also includes where theengine air amount parameter is adjusted based on a blow-through airestimate.

In one example, the method includes where the engine air amountparameter is a cylinder air amount estimate and where the cylinder airamount estimate is increased when an engine temperature transitions froma lower temperature to a higher temperature, and where the enginetemperature is a temperature of a valve of a cylinder. In this way,changes due to valve temperature may be compensated. The method alsoincludes where the engine actuator is an ignition coil, and where theoutput of the ignition coil is a spark timing. The method also includeswhere the engine actuator is a throttle, and where the output of thethrottle is a position of a throttle plate. The method further comprisesadjusting a blow-through amount in response to a rate of change ofcylinder air amount.

As will be appreciated by one of ordinary skill in the art, the methoddescribed in FIGS. 3 and 6 may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various steps orfunctions illustrated may be performed in the sequence illustrated, inparallel, or in some cases omitted. Likewise, the order of processing isnot necessarily required to achieve the objects, features, andadvantages described herein, but is provided for ease of illustrationand description. Although not explicitly illustrated, one of ordinaryskill in the art will recognize that one or more of the illustratedsteps or functions may be repeatedly performed depending on theparticular strategy being used.

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description. For example,single cylinder, I2, I3, I4, I5, V6, V8, V10, V12 and V16 enginesoperating in natural gas, gasoline, diesel, or alternative fuelconfigurations could use the present description to advantage.

1. A method compensating for thermal conditions during transient engineconditions, comprising: adjusting an engine air amount parameter and acylinder residual gas amount in response to a rate of change of cylinderair amount, the engine air amount parameter and cylinder residual gasamount adjusted via an engine MAP and cylinder air amount volumetricefficiency relationship; and adjusting output of an engine actuator inresponse to the engine air amount parameter.
 2. The method of claim 1,where the engine actuator is a fuel injector, and where the engine airamount parameter is based on a curve empirically determined from aplurality of engine MAP and cylinder air amount readings, and where theengine air amount parameter is one or more of a cylinder air amount anda blow-through air amount.
 3. The method of claim 1, where the engineair amount parameter is adjusted in response to a curve representingengine volumetric efficiency in a MAP versus cylinder air amount space,and where the curve accounts for residual exhaust gas.
 4. The method ofclaim 3, where the engine actuator is an air inlet throttle, and furthercomprising adjusting a position of an EGR valve in response to thecylinder residual gas amount.
 5. The method of claim 1, where the rateof change of cylinder air amount is determined via a difference betweenan air flow rate and a filtered air flow rate.
 6. The method of claim 5,further comprising adjusting the engine air amount parameter in responseto engine cam timing.
 7. The method of claim 1, where the engine airamount parameter is a cylinder air amount estimate and where thecylinder air amount estimate is reduced when an engine temperaturetransitions from a higher temperature to a lower temperature, and wherethe engine temperature is a temperature of a valve of a cylinder, andwhere the cylinder air amount estimate is reduced as time increasesafter a transient emulating a valve thermal transient.
 8. A methodcompensating for thermal conditions during transient engine conditions,comprising: adjusting an engine air amount parameter and a cylinderresidual gas amount during a condition of blow-through in response to arate of change of cylinder air amount; and adjusting an output of anengine actuator in response to the engine air amount parameter.
 9. Themethod of claim 8, where the condition of blow-though is estimated froma difference between a total cylinder air mass flow curve and avolumetric efficiency curve.
 10. The method of claim 8, where the engineair amount parameter is adjusted based on a blow-through air estimate.11. The method of claim 8, where the engine air amount parameter is acylinder air amount estimate and where the cylinder air amount estimateis increased when an engine temperature transitions from a lowertemperature to a higher temperature, and where the engine temperature isa temperature of a valve of a cylinder.
 12. The method of claim 8, wherethe engine actuator is an ignition system, and where the output of theignition system is a spark timing.
 13. The method of claim 8, where theengine actuator is a throttle, and where the output of the throttle is aposition of a throttle plate.
 14. The method of claim 8, furthercomprising adjusting a blow-through amount in response to a rate ofchange of cylinder air amount.
 15. An engine system, comprising: anengine; a turbocharger coupled to the engine; and a controller includinginstructions for adjusting an engine air amount parameter and a cylinderresidual gas amount in response to a rate of change of cylinder airamount flow during blow-through conditions with positive intake-exhaustvalve overlap and non-blow-through conditions without positiveintake-exhaust valve overlap, the controller including furtherinstructions for adjusting an actuator in response to the engine airamount parameter.
 16. The engine system of claim 15, where the rate ofchange of cylinder air amount flow is determined from a differencebetween engine air flow and filtered engine air flow.
 17. The enginesystem of claim 15, further comprising additional instructions foradjusting the engine air amount parameter in response to cam timing. 18.The engine system of claim 15, further comprising additionalinstructions for adjusting the engine air amount parameter in responseto engine speed and engine load.
 19. The engine system of claim 18,further comprising additional instructions to determine blow-throughduring cylinder air flow conditions where cylinder air flow is greaterthan a cylinder air flow at an intersection of a maximum volumetricefficiency curve and a non-blow-through curve.